I'm working with a large dataset, and I accidently changed a string field to 'Date/Time', and I can't change it back. I'm working in the browser version of ArcInsights, and it could be an error with my system.
You have a couple of options in this scenario. Obviously, if you catch it right away, the undo tool works on data type changes but I'm assuming we're past that point 😀.
The best option then is to combine the time components back into a new String field using the CONCATENATE Function.
If using ArcGIS Insights Desktop, you could also use the Data Engineering workbook to change the field type.